we have z = e^(((2pi)/7)i)
a = z+ z^2 + z^4 and b = z^3 + z^5 +z^6
we know a + b = −1 and 1−b=a
find S = cos(((2pi)/7))+ cos(((4pi)/7)) + cos(((8pi)/7))
thanks for help
consider the circle
(x−1)^2 +(y−1)^2 =2,
A(1,4), B(1,−5). if P is
a point on the circle such that
PA+PB is maximum then
prove that P,A,B are collinear
points.
On dispose de N+1 urnes.l′urne U_k
contient k boules blanches et N−k boules
noires.on tire successivement sans
remise n boules de l′urne et on note
An l′evenement ′′choisir n boules noires
lors des n premiers tirages′′. Determiner
P(An). on notera U_k =′′choisir l′urne k′′